Optical networks transport optical signals. An optical network usually includes nodes and spans, for example fiber spans or other optical transmission media. Digital optical signals having multiple states, for example one state representing a logic “1” and one state representing a logic “0”, are generally transported, optically, between two adjacent nodes across a fiber span. Once a digital optical signal reaches a node at the end of the fiber span, it is usually converted into a digital electrical signal for content processing.
Optical communication systems or networks must be able to maintain a good quality of digital optical signals during transportation. Hereinafter, the terms “optical signal” and “digital optical signal” may be used interchangeably with both meaning a binary digital optical signal having one state representing a logic “1” and one state representing a logic “0”. In recognizing the need for high quality optical signal, which may include for example power level and extinction ratio of the optical signal, various efforts have been devoted so far toward developing optical signal processing devices that may be used to manipulate and/or control the optical signal in the optical domain.
An optical amplifier is one such device that may be used to enhance the power level of an optical signal. However, there are currently no optical devices that can improve the extinction ratio, a ratio of power of the state of logic “1” over the state of logic “0”, of an existing optical signal without first converting it into an electrical signal. Such an optical signal power handling device or “optical signal discriminator”, as may be referred to hereinafter, will play a major role in both current and future optical signal processing technologies by virtue that the optical signal discriminator has the capability of reshaping and reconstructing original digital information in the optical domain. In the meantime, by improving the extinction ratio of an optical signal, an optical signal discriminator may be able to greatly improve receiver sensitivity of a node, in an optical network, that receives the digital optical signal, resulting in a low bit-error-rate and high fidelity of optical signal transmission.